Fuel injection valves of this kind are known from WO 2007/098621 A1, for example. Fuel injection valves of this kind allow both controllability of the opening movement of the injection valve member and a rapid closing process of the injection valve member with minimum assembly effort. Implementing multiple injections at very short intervals is possible. While the control space and the valve space are connected continuously to one another only via a precise restrictor passage, an intermediate valve otherwise separates these two spaces continuously from one another. A high-pressure feed connected to the high-pressure space of the injection valve and leading into the control space, said feed being of large cross section in comparison with the cross section of the restrictor passage, is controlled by the intermediate valve. Since the cross section of the outlet from the valve space, which outlet is controlled by an electric actuator arrangement, can also be significantly larger than the cross section of the restrictor passage, the opening movement of the injection valve member is dependent substantially exclusively on the cross section of the restrictor passage. When the outlet from the valve space is closed by means of the actuator arrangement, the intermediate valve opens quickly and exposes the large cross-section passage connected to the high-pressure space, bringing about rapid ending of the injection process.
The intermediate valve member of the intermediate valve is of mushroom-shaped design and has a stem, which is guided with a close sliding fit in a guide passage of an intermediate part, and a head, which, in the closed position of the intermediate valve member, rests by means of a sealing surface extending at a radial distance around the stem on an annular intermediate valve seat formed on the intermediate part.
It has been found that, when the high-pressure feed is completely closed and there is therefore surface contact between the sealing surface of the head and the surface of the intermediate valve seat, high adhesion forces may be in effect, possibly making reopening of the intermediate valve to end the injection process more difficult, wherein the accurate timing of the ending of the injection process, in particular, may be impaired.
This adhesion problem is already discussed in document WO 2010/088781 A1. To solve the problem, it is proposed to leave a restricted fluid connection between the high-pressure feed and the sliding fit of the stem on the intermediate part in the closed position of the intermediate valve. For this purpose, the sealing surface of the head and the sealing surface of the intermediate valve seat are designed to slope relative to one another in such a way that, in the closed position of the intermediate valve, they rest sealingly on one another radially on the outside and, radially on the inside, form a restrictor gap which widens in the axial direction for restricting the high-pressure feed in the direction of the valve space. The aim is therefore an annular linear seal between the valve member and the valve seat of the intermediate valve. The extremely precise production of the mushroom-shaped intermediate valve member and of the intermediate part interacting therewith for this solution is extremely delicate and very expensive.
Furthermore, this document discloses embodiments of the fuel injection valve in which the intermediate part and an intermediate element resting on the latter on the side facing away from the guiding part are of circular disk-shaped design and are arranged in a housing section which is almost fully circular-cylindrical on the inside. Between them and the housing, they leave free a section of the high-pressure space. On the one hand, this section is connected to the injection valve seat and, on the other hand, it is connected to the high-pressure fuel inlet. The connection to the high-pressure inlet can be made, for example, by the formation of recesses extending outward in a radial direction and obliquely to the longitudinal axis in the otherwise cylindrical section of the housing. Such recesses weaken the stability of the housing, e.g. of the nozzle body, in this region, requiring a correspondingly thicker design of the housing wall.
Document US 2011/0233309 A1 discloses a fuel injection device in which a pressure surface of a pressure element presses against an opening wall surface in order to interrupt a connection between an inflow port and a pressure control chamber when a connection is established between an outflow port and a return channel by a pressure control valve. The pressure surface of the pressure element is displaced or separated from the opening wall surface in order to open the inflow port in the opening wall surface to the pressure control chamber when the connection between the outflow port and the return channel is interrupted by the pressure control valve. The pressure surface of the pressure element or the opening wall surface of the control housing is provided with a depressed inflow section and a depressed outflow section, which are separated from one another. A depressed dimension of the depressed inflow section is larger than the depressed dimension of the depressed outflow section.